Casualties and damage resulting from “friendly fire” are an increasing concern on the modern military battlefield. That is, if a soldier, vehicle, or installation is misidentified as hostile by the troops on the same side, there may be an attack before the misidentification can be discovered. This problem arises in large part because of the increasing reliance on sensors rather than visual recognition to identify objects, and the rapidity with which an attack may be performed.
Historically, friendly-fire incidents were avoided largely through visual identification of objects by the attacker. Also, because attacks were mounted over a period of time, there was usually an opportunity to correct early identification errors. The reliance on automated sensor technology and the rapid pace of an attack in modern warfare has partially negated these traditional controls. More recently, there has been a reliance on radio communications between different elements of a force to guard against friendly-fire casualties and damage. Radio communication to avoid such situations has many drawbacks, including the opportunity for confusion between the source of a radio message and a physical object, stealth considerations in avoiding disclosure of a location and intentions by both the interrogating party and the interrogated object, and the use of countermeasures by the enemy.
Advanced, technology-intensive techniques such as the use of laser radar are under consideration, but are in many cases impractical for widespread use such as by every friendly soldier on the battlefield due to size and cost considerations. On the other hand, inexpensive, low-technology techniques such as the use of distinctive light-reflective patches or active light reflectors affixed to personnel or equipment may be widely used, but they are less secure in that they may also be easily copied or appropriated by the enemy to mask its activities.
There is a need for a friend-or-foe identification system that is highly reliable and secure and is difficult for an enemy to appropriate or mimic, yet is sufficiently inexpensive, light in weight, and compact to allow its widespread utilization. The present invention fulfills this need, and further provides related advantages.